Dual screw drive



March 3, 1953 F, '[ERmNA 1 2,630,022

DUAL SCREW DRIVE Filed 0st. 26. 1951 l 24 /6 Z6 Q// 2/ @j /Z -Msln 50 @n/f l 'Il 3,5 Z 5*/ I" Z0 Z9 L 30 EZ 71 'llldrllll Il: 'h

IN VEN TOR.

AGEA/7" Patented Mar. 3, 1953 DUAL SCREW DRIVE Frank Terdina, Seattle, Wash., assignor to Boeing Airplane Company, Seattle, Wash., a corporation of Delaware Application October 26, 1951, Serial No. 253,414

2 Claims. (C1. 'i4-424.8)

This invention relates to a dual screw drive with both the screw and nut independently driven.

The invention comprises a screw rotatably mounted, a power unit to lrotate the screw through a worm gear drive, a nut and a nonrotatable housing separated by a thrust bearing and mounted for travel along the screw, another power unit to rotate the nut through a worm gear drive, the power unit moving axially with the housing, and mounting projections on the housing to receive connecting rods extending to movable elements.

The purpose of the invention is to provide a compact dual drive screw having both a high translation speed and a high degree of reliability.

An object of the invention is to provide a dual drive screw with each drive capable of operating the entire assembly in the event of failure of the other unit.

A further object of the invention is to provide a dual drive screw which can only be reversed by the power operation of the worm gear drive or drives.

The purpose and objects of the invention will become more apparent as the following description is read in conjunction with the drawings in which like numbers designate the same part throughout the several views:

Figure l is a partial perspective view of the operational end of the dual drive screw, and

Figure 2 is a half-sectional view taken on the screw centerline.

More particularly, the invention comprises a rotatable screw I mounted on thrust bearings I I secured to a structure, a driven gear I2 keyed I3 to the screw I@ adjacent the thrust bearing Il, a power unit i4 mounted on the thrust bearing support I5, a worm gear i6 to transmit power from the unit I i to the driven gear I2, sleeve member II composed of the nut i3 and the housing I9, connected through a thrust bearing assembly 2!) for movement along the screw I0, a second driven gear 2l made integral with the nut I8, a second power unit 22 mounted on the housing I9, a second worm gear 23 to transmit power from the unit 22 to the driven gear 2 I, mounting projections 24, 2-'5 on the housing I9 to receive connecting rods 26, 21 extending to movable elements (not shown), and a restraining-supporting member 23 attached to the structure to support the housing I9 by receiving the projection 25 and rod 21 and to restrain the housing I9 from rotational movement.

The threads 29 are of the ball bearing type 2 permitting rapid translation when both power units I and 22 are operating. The thrust bearings used are composed of the circular races 30, balls 3| and cover portions 32 secured by machine screw fasteners 33. (Radial bearings are not shown.)

In operation, when power is supplied to the unit I4 to rotate the screw I0 the sleeve member I1 moves along the axis of the screw i0. As power is simultaneously supplied to the unit 22 to rotate the nut I8 of the sleeve member I1 in the opposite direction, the speed of translation is accordingly increased. The power to unit I4 may be stopped and the translation will continue under the power of unit 22.

The housing I9, restrained from rotary movement by the member 28, travels along the screw axis to move connecting rods 26, 2I which in turn control the positioning of movable elements (not shown) su-ch as stabilizers for aircraft. Where the travel along the screw axis is limited, the power screw may be supported at only one end and the housing suspended from a hinged support (not shown).

By utilizing the inventive dual screw drive the following advantages are realized: the latent safety feature of continued operation when one power unit fails, and the compactness of the assembly reducing the space requirement attributed to a larger single power unit assembly having comparable performance characteristics.

I claim:

1. A dual drive screw assembly comprising the structure and movable elements of an airplane, a power screw mounted on the said structure, bearings supporting the said power screw, a power unit mounted at the said bearing support, a worm gear assembly to transmit power from the said power unit to the said screw, a non-rotatable housing, a nut interconnected with the said housing and threadably engaging the said screw, a thrust bearing separating the said housing and the said nut, a second power unit mounted on the said housing, a worm gear unit to transmit power from the said second power unit to the said nut, mounting projections on the said housing, connecting rods secured between the said projections and said movable elements, and a restraining member attached to the structure preventing the said housing from rotating.

2. A dual drive screw comprising mountable thrust bearings, a power screw supported by the said thrust bearings, a power unit integrally mounted on the support of the said bearings, a worm gear assembly to transmit power from the yNumber '4 be moved for transmitting the motive power, and a restraining member preventing the housing from rotating.

FRANK TERDINA.

REFERENCES CITED The following references are of record in the leof `this patent:

UNITED STATES PATENTS Name Date .2,333,341 Scrivener Nov. 2, 1943 

